Vehicles with
variable steering characteristics have long been studied and compared with
those having typical fixed gear ratio steering, and the variable gear ratio
properties are reported to have improved maneuverability and stability in
high-speed lane changes and on slippery low-friction road surfaces. However, it
is not clear how gear ratios should be set for individual vehicle characteristics.
Therefore, the present study has investigated a variable steering gear system
using body slip angle feedback for the purpose of improved maneuverability and
stability in the critical cornering range and upwards, in excess of the
critical limit, and into the countersteer range. The results of a driving
simulator experiment show that the steering effect improves and maneuverability
and stability increase in the critical cornering range and upwards, in excess
of the critical limit, and into the countersteer range by applying
linear-variable control to the steering ratio from a body slip angle of 5?.
This result is seen both in double lane changes, such as in hazard avoidance,
and in J-turns with long drifting. Moreover, it shows an improvement in drift
controllability through prompt countersteering. Overall, the present system can
enhance the driver’s hazard avoidance capability.